Intro4u2u

Three different bonnet/stem designs are predominant in gate valve construction. They are: inside screw, rising stem (ISRS), non-rising stem (NRS), and outside screw and yoke (OS&Y).

* The ISRS bonnet/stem design is the most popular design in use today on bronze valves. Due to the fact that it exposes the stem threads to the process fluid and potential corrosion damage which could cause a stem to disc failure, the ISRS design is not used for critical service industrial applications.
* The NRS type is another special purpose type that is used in applications where there is limited vertical clearance above the handwheel, because on an NRS valve, the stem does not rise up as the valve is opened. Most NRS valves today are manufactured of either iron or bronze. Some applications such as marine use, where clearances are tight, often use NRS steel gate valves.
* The most common stem/bonnet design in use on industrial valves is the OS&Y. The OS&Y design is preferred for corrosive environments because the threads are outside the fluid containment area. It also differs from other designs in that the handwheel is attached to a bushing at the top of the valve yoke, and not to the stem itself, thus the handwheel does not rise as the valve is opened.

Also in the gate valve family are knife and sluice gates. The bonnetless knife gate is especially suited for use in slurries such as in pulp and paper mills. Knife gates are very thin, only slightly wider than there closure element (disc). Because of their unique geometry and thin cross-section, knife gates are limited to low pressure applications.

In appearance, the sluice gate doesn’t look like it even belongs in the gate valve family, however based upon its sliding disc design; it is characterized as a gate valve. Sluice gates are limited to very low pressures, in most cases, simple head pressure. They are used primarily in waste water and irrigation systems.
Valve Standards

Gate valves standards are produced by several standards making organizations, for a multitude of industries. Here are some of the better known gate valve specifications:

American Petroleum Institute
*API 600 “Steel Gate Valves, Flanged & Buttwelding Ends”, it is a companion document to ISO 10434.
*API 602 “Compact Steel Gate Valves”
*API 603 “Corrosion Resistant Bolted Bonnet Gate Valves”
*API 6D “Specification for Pipeline Valves”, it is a companion document to ISO 14314.

Manufacturers Standardization Society
*SP-70 “Cast Iron Gate Valves”
*SP-80 “Bronze Gate, Globe, Angle and Check Valves”
*SP-81 “Stainless Steel Bonnetless, Flanged, Knife Gate Valves”

American Waterworks Association
*AWWA C500 “Metal-Seated Gate Valves for Water Supply Service”
*AWWA C509 “Resilient-Seated Gate Valves for Water Supply Service”
*AWWA C515 “Resilient-Seated Gate Valves for Water Supply Service”

American Society of Mechanical Engineers
*B16.34 “Valves- Flanged, Threaded and Welding End”